Fire Forests of the Cascades

The Gnarl Fire of 2008 shocked Portlanders by racing across the east slopes of Mount Hood, and nearly destroying the historic buildings at Cloud Cap and Tilly Jane. But as an east side fire, the Gnarl burn was relatively small, and part of what has become an annual ritual for rural communities of fighting intense blazes along the east slope of the Cascades.

The 2008 Gnarl Fire, viewed in August from Dufur Mill Road

The cause for the intensity of these fires is well-known and well-documented. We know that a century of fire suppression, promotion of even-aged stands of second growth in logged areas and a changing climate are forces conspiring to burn the east side forests on a scale not seen in recent decades.

But not all of the east side fires are catastrophic, even with the fuel build-up from our history of fire suppression. The 2006 fire at Bluegrass Ridge was a glimpse into what was once a routine occurrence along the east side of the Cascades. The Bluegrass Fire began as a lightning strike in the dry season, and soon spread along the east face of the ridge in a mosaic pattern: some parts of the forest were completely killed, while others were a mix, where pockets of forest survived among the burned trees.

The aftermath of the 2006 Bluegrass Fire ranged from total destruction in areas like this, to mosaic patterns where less crowded forests existed

Most significantly, the larger, fire-resistant species like western larch and ponderosa pine often survive fires in these mosaic areas, and this was the case in the Bluegrass Fire. We will know in a year or two whether the extensive larch population in the Gnarl Fire area were similarly resistant.

The survival of these big trees is the key to the natural ecosystem that defines east side forests. Forest ecologists are now calling these east side regimes “fire forests”, as a counterpoint to the west side rain forests, where abundant rainfall is the operative element in defining the forests.

The “fire forest” name is apt, since we now know that a number of tree species in this dry forest system depend on fire for natural succession that creates mature forests. In the Mount Hood area, these east side trees are Douglas fir, western larch and ponderosa pine. All three have thick, fire-resistant bark that helps them survive moderate fires, and benefit from periodic clearing of undergrowth that competes for moisture and soil nutrients. Fires, in turn, release nutrients for the big trees, further enhancing the growth of fire-resistant species.

Western larch light up the eastside forests in autumn. Larch are among the fire-resistant species that require periodic burns for their long-term health

The question for the east side forest is not whether they will continue to burn — they have evolved with fire, after all — but rather, how we will learn to live with the fires. We now know that we cannot simply extinguish them. A century of fire suppression has created mammoth fires that we simply cannot control.

We also know that we cannot prevent forest fires from starting, since the large majority begin from lighting strikes. And we know that many more catastrophic burns will occur before the east side forests return to a more sustainable condition that mimics the natural ecosystem that once thrived.

Most ominous is the recent discovery — from tree-ring research — that the Western states are coming off an unusually wet century, and that the decades ahead are likely to carry more drought, not less. So it is imperative to help the east side forests stabilize before conditions make that proposition still more difficult.

These mature, healthy forests of western larch, ponderosa pine and Douglas fir along Bluegrass Ridge survived the fire

A first step is continuing to thin tree plantations on logged lands to help prevent still more crowded, bug-infested forests like those that are currently driving the fire epidemic. The second step is more difficult: letting fires burn. This policy will be most difficult in the many areas where rural development has encroached on forest boundaries, but it is a necessary step. Both of these steps will require a new mindset about fire, not the least of which will be a public education shift away from Smokey Bear and fire suppression and toward a modern understanding of fire.

But a third step is most difficult of all: setting fires in prescribed locations to help restore forest balance. While the rash of east side fires in recent years has made this part of restoring forest balance less urgent, it will still be necessary — and controversial. Federal agencies have already begun employing this tool, but in cases where a controlled burn becomes a wildfire, the public is not prepared to understand why that risk is necessary — and perfectly natural. Still more public outreach and education will be needed.

The good news is that the scientists are winning this debate, and even the Forest Service has gradually begun to embrace fire ecology as part of their management philosophy. The Park Service is much further long, having successfully weathered the early criticism of their prescient decision to let the huge Yellowstone fires of the mid-1980s burn.

The remarkable resilience and recovery of Yellowstone in the intervening years has not only been vindication for that bold decision, but also an invaluable lesson to land agencies across the west who are responsible for managing “fire forests”. The time to embrace fires in our forests has arrived.